Processing chambers, such as chemical vapor deposition ("CVD") chambers are used to process work pieces, such as semiconductor wafers, light crystal diodes, flat panel displays, or other similar substrates. During processing, a substrate located within the processing chamber is exposed to reactive gases introduced into the chamber and the substrate has material deposited on it. During the processing of the substrate, the inside surfaces of the chamber itself are typically contaminated by residual deposited material. Thus, in subsequent processing of substrates within the contaminated chamber, unwanted particles may form when the reactive gases combine with the contamination on the chamber's surfaces and the particles may be deposited on the substrate. Thus, processing chambers must be periodically cleaned to avoid the contamination of the substrates being processed.
Typically, processing chambers are in situ (automatically) cleaned using a gaseous cleaning agent, activated with a plasma. In conventional processing chambers, the cleaning agent gas is introduced into the processing chamber in the same manner as the reactive gases are introduced during processing, e.g., through a gas inlet port, such as a showerhead. Conventional processing chambers typically include a chuck that supports the substrate and is positioned under the showerhead. During processing, the reactive gases flow out of the showerhead and over the substrate located on the chuck. The unused reactive gases are then pumped out of the chamber through an exhaust port. Similarly, during a cleaning cycle, the gaseous cleaning agent flows out of the showerhead and over the chuck. The gaseous cleaning agent is then pumped out of the chamber through the exhaust port. Thus, the gaseous cleaning agent has approximately the same flow pattern as the reactive gas. As the gaseous cleaning agent is pumped through the chamber, the gaseous cleaning agent contacts the chamber's interior surfaces and reacts with the contaminants on the chamber's surfaces to create a gaseous by-product, i.e., vapor, and particles of the contaminant. The vapor and particles of the contaminant are then pumped out of the chamber along with the remaining gaseous cleaning agent through the exhaust port.
Where the cleaning process uses a plasma, radio frequency (RF) power is provided within the processing chamber, forming a plasma to ionize the cleaning agent gas to enhance chemical reaction with the contamination on the chamber's interior surfaces. The RF power is typically applied between the showerhead and the chuck. Thus, the gaseous cleaning agent does not form a plasma until the gas has flowed out of the showerhead and into the RF field.
Unfortunately, contamination of the chamber can occur not only on the walls and chuck of the chamber, but also on the interior walls of the showerhead. This is particularly true where a non-plasma type process is being used, such as a parylene process. There are many forms of parylene, such as parylene C, parylene N, and parylene AF4, by way of example. Parylene AF4 is the form best suited and, thus, typically used for VLSI semiconductor devices. Parylene polymer is a dielectric material that will deposit on surfaces below 50.degree. C. During processing, parylene is often deposited on the interior walls of the showerhead. Other CVD processing chambers, such as tungsten, titanium nitride, or similar non-plasma processes, can also undergo undesirable deposition of the material within the showerhead.
Cleaning a parylene processing chamber, or other such processing chamber, with a plasma activated cleaning agent does not adequately clean the interior of the showerhead. Consequently, the interior of the showerhead has to be replaced or periodically cleaned manually, thereby increasing deposition tool downtime. Consequently, the overall throughput of the deposition tool is decreased.
Thus, an in situ plasma clean is needed for processing chambers that can clean the interior surfaces of the chamber including the interior of the showerhead.